1. Field of the Invention
The present invention relates to a high-rate coding device for performing high-rate coding of an input signal, a video signal recording and reproduction apparatus for recording and reproducing data obtained by the high-rate coding and to a video signal transmitting apparatus for transmitting data obtained by the high-rate coding. (In this specification, high efficiency coding and high efficiency decoding are expressed as "high-rate coding" and "high-rate decoding".)
2. Description of the Related Art
Video signal recording apparatuses for digitally recording a video signal are generally classified into two types: One type of apparatuses compress a standard-definition (SD) TV signal to 25 Mbps by performing intra-frame coding for recording. The other type of apparatuses compress a high vision signal to 50 Mpbs for recording. In these types of apparatuses, the type of video signals usable for input and output and the quality of the signals obtained are limited. It is extremely difficult to record and reproduce a video signal which is of a different type from the signal which are input to or output from devices in the video signal recording apparatus without significantly changing the recording and reproducing processing.
For example, in a video signal recording apparatus which receives a digital TV signal obtained by interlaced scanning (hereinafter, referred to as an "interlaced scan TV signal") and compresses such a signal for recording, two successive fields of the interlaced scan TV signal are combined and converted into one frame of a progressive scan TV signal (a TV signal obtained by progressive scanning) before performing compression and recording. In the case when a progressive scan TV signal is used as an input signal, the input signal is already framed, and the frame cycle is 1/2 of the cycle of an interlaced scan TV signal. Such a progressive scan TV signal cannot be recorded by a conventional video signal recording apparatus.
In a video signal recording apparatus which receives a progressive scan TV signal and compresses such a signal for recording, the progressive scan TV signal is switched frame by frame to be sent to two channels. By such switching, data corresponding to one frame of the progressive scan TV signal is processed with high-rate coding to have the same quantity of codes as obtained by high-rate coding of data corresponding to one frame of an interlaced scan standard-definition TV signal including two successive fields. The data obtained by the high-rate coding is recorded in the same number of tracks as used for recording data corresponding to one frame of an interlaced scan TV signal.
In such a method, however, the data processing is performed frame by frame. Accordingly, recording of a still image cannot utilize the correlation between data corresponding to different frames, thus preventing improvement in the coding efficiency. Further, since the data is divided into two channels, time delay occurs between images which are output from different channels. Due to such time delay, data corresponding to different frames are arranged by turns, resulting in deterioration in the quality of an image obtained in a search picture mode.
Moreover, in order to perform high-rate coding of a signal including a standard-definition TV signal defined by 4:2:2 (hereinafter, referred to as a "4:2:2 signal") conforming to the studio standards described in CCIR Recommendation 601-1 and an auxiliary signal of a luminance signal required for progressive scanning, the conventional dividing method is not suitable for the following reason: By the division performed by the conventional dividing method, the number of effective pixels of the data corresponding to a color difference signal of the resultant signal is decreased, and thus ICs in the conventional video signal recording apparatus cannot be used for high-rate coding.
In conventional high-rate coding devices for performing high-rate coding and conventional video signal transmitting apparatuses for transmitting a video signal coded by the conventional high-rate coding devices, the type of the image signal usable for input and output and the quality of the resultant signal are limited. Accordingly, it is extremely difficult to change the specifications of such apparatuses and the characteristics of the resultant signals without significantly changing the high-rate coding processing, data recording processing, and the like.
Shuffling is one method used for performing high-rate coding in the conventional video signal recording apparatus for compressing a TV signal to be recorded in a magnetic tape. By shuffling, an image plane is divided into a plurality of areas. A prescribed number of blocks are obtained from prescribed positions of each area to form a coding unit for high-rate coding. For a high-definition (HD) TV signal, there are three systems regarding the number of the scanning lines and the field frequency: 1125 scanning lines/60 Hz, 1050 scanning lines/60 Hz, and 1250 scanning lines/50 Hz. In this specification, the system corresponding 1125 scanning lines and 60 Hz, for example, will be referred to as the "1125/60 system". In the case when a signal of the 1125/60 system is used, shuffling is very complicated and thus requires a large circuit for shuffling.